# Ratio Test

The ratio test is a test for determining whether a series converges. It is used for calculating the radius of convergence for power series.

Ratio test is a college-level concept that would be first encountered in a Calculus II course. It is an Advanced Placement Calculus BC topic and is listed in the California State Standards for Calculus.

### Prerequisites

Power Series: | A power series is a sum of powers of a variable. A power series is essentially an infinite polynomial. |

Radius of Convergence: | The radius of convergence of a power series is half the width of the interval inside which it converges absolutely. |

Taylor Series: | A Taylor series is a power series of a function around a given point. |